This invention relates to novel 2-(alkoxymethyl)pentane-1,5-diisocyanates and processes for their preparation and use. This invention further relates to the preparation of plastics via the polyisocyanate addition polymerization process using these novel diisocyanates, as well as 2-(alkoxymethyl)-pentane-1,5-diurethanes and 2-(alkoxymethyl)pentane-1,5-dicarbamic acid chlorides, which are particularly suited as starting components in the preparation of 2-(alkoxymethyl)-pentane-1,5-diisocyanates.